AG-2 and AG-3 are recently discovered human homologues of the secreted Xenopus laevis proteins XAG-1/2 (AGR-1/2) that are expressed in the cement gland, an ectodermal organ in the head associated with anteroposterior fate determination during early development(1). Although the roles of AG-2 and AG-3 in mammalian cells are unknown, both proteins share a high degree of protein sequence homology and lie adjacent to one another on chromosome 7p21.